All of my original stories on here, including the halloween/holiday oneshots, are from the same universe, most characters are connected in some fashion. So, for me, writing down a plot bunny has a good chance of being usable, even if it’s a spinoff story. But yep, recording them helps retain them and you can go back, even with a fickle muse … may be a challenge.
And sometimes, those ideas are rejected, not because they’re lousy, but because it’ll distract too much from the major thrust to the story, or simply overwhelm it. (I recently pruned what would’ve been chapter 16 from Dale’s Game because it was too much, even though the underlying premise was sound in terms of what the characters needed in skill improvements. Sad to remove 5kwords and start the chapter over….not really removed, I do save them off into a separate file, just in case.)